Electron discharge devices using grid control scanning



Jan. 5, 1960 H. R. BEURRIER 2,920,231

ELECTRON DISCHARGE DEVICES USING GRID CONTROL SCANNING Filed Aug. 27,1956 4 Sheets-Sheet 1 1 ze IIIIIIIIIIIIII lllll l/VVENTOR H. R. BEURR/ERBY %MSVD'QLQ/QQ ATTORNEY Jan. 5, 1960 H. R. BEURRIER 2,920,231

ELECTRON DISCHARGE DEVICES usmc GRID CONTROL SCANNING Filed Aug. 27,1956 4 Sheets-Sheet 2 Pm 20 F/GZ 1- a? 2/ F/a 4 I I o d INVENTOR By HJQ.BEURR/ER WJQWQQ A TTORNEV Jan. 5, 1960 H. R. BEURRIER 2,920,231

ELECTRON DISCHARGE DEVICES USING GRID CONTROL SCANNING Filed Aug. 27,1956 4 Sheets-Sheet 3 FIG. 5

VERTICAL sweep GENERATOR 2%? HORIZONTAL PULSE GENE/M TOR \54 BIAS s PPLVVIDEO V COMPENSATOR MM/HER FIG. 8

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12 Claims. (Cl. 31S30) This invention relates to electron dischargedevices and particularly to grid controlled scanning of an electron beamin electron discharge devices.

-In the conventional type of cathode ray tube as utilized, for example,in television applications, the position of the electron beam and hencethe particular area of the target impinged by the beam at any instant,is determined by the intensity of deflecting fields established inelectrostatic or electromagnetic deflection systems. The utilization ofsuch deflection systems requires employment of the familiar electron gunwith its attendant accelerating and focusing electrodes to form andproject a suitable electron beam through the deflecting field. Suchelements demand an appreciable tube length for effective operation, thushindering the use of cathode ray tubes in limited space applications.

The instant invention provides a unique grid control of electronsemitted from the cathode so as to eliminate conventional beam formingand deflecting elements. The entire output of a large cathode surface isreceived at the grid structure which, in accordance with this invention,directs the passage of electrons through portions of the grid allowingonly a controlled portion of the electrons to reach the target screen.

By utilizing a cathode surface substantially as large as the targetdisplay surface, the electron emission may be controlled by the gridstructure to provide a suitable scanning raster for various applicationssuch as television, sonar and multiplex code conversion.

Accordingly, it is an object of this invention to provide an improvedelectron discharge device.

It is another object of this invention to provide a compact electrondischarge device which contains few components.

It is a further object of this invention to provide grid control of anelectron beam in lieu of electrostatic or electromagnetic deflection.

These and other objects of the invention are attained, in accordancewith the invention, by the provision of a series of grids in anevacuated chamber between a flooding beam cathode and a target anodedisplay surface, the elements all being of substantially like planardimensions. The grid structure performs the essential positioningcontrol of the electron beam on the display surface and may be adaptedto modulate the beam intensity as well in applications requiring suchcontrol.

In conventional cathode ray tube operation, the electron gun normallyprovides a fine pencil shaped beam which may be deflected in horizontaland vertical coordinates so as to impinge the target anode at anydesired discrete area. With a regularly graduated deflection program, asnormally employed in television applications, for example, the beam maybe scanned over the target surface in a predetermined raster.

I have found, in accordance with one aspect of this invention, that suchscanning may be performed by a grid structure comprising a pair ofadjacent grids foreach deflection coordinate, each including a series offine paralatent to produce a linear potential gradient across theindividual grid Wires in the plane through which the positioning is tobe controlled. By applying voltage of op posite polarity to theresistance members of each of a pair of the grids, oppositely directedlinear potential gradients will be established thereacross.

The grid structure will allow electrons from the cathode to passtherethrough to the target anode only in those areas where the gridwires exhibit a positive potential. Thus, by appropriate settings of thepotential gradients on the various grids relative to cathode potential,electrons may be channeled through the grid structure to impinge thetarget anode in a desired discrete area. Also, by varying the potentialgradients according to a uniform program, the restricted electron pathmay be altered in a regulated pattern so as to scan an electron beamabout the target anode.

In accordance with another aspect of this invention, the

grid structure may constitute a portion of a voltage pulse delay line inwhich the individual grid wires act as a distributed inductance. Bybiasing the grid to cut oif electron flow and applying a pulse to thedelay line of sufficient amplitude to bring the tube out of cutoff,electrons may be scanned across the-target anode as the voltage pulsemoves down the delay line.

- Additionally, a mode of intensity modulation may be performedutilizing the grid structure in accordance with this invention wherebyvariations in the potential gradients relative to cathode potentialapplied to pairs of grids will permit consequent variations in theportion of the electron beam reaching the target anode.

It is a feature of this invention to position a pair of coordinate gridstructures in the path of electron flow, which grid structures comprisemutually parallel grid wires connected in each individual grid to acommon conductive element.

It is another feature of this invention that oppositely directed linearpotential gradients be applied to the conductive elements of the pair ofcoordinate grid structures.

. It is another feature of this invention to employ a pair of gridstructures for each deflection coordinate.

It is another feature of this invention so to vary relative positions ofthe potential gradients on each grid structure effectively to confinethe electron beam to impinge the target electrode in a discrete area andto scan the impinging portion of the beam over the target electrode. Y

It is another feature of this invention so to vary the cathode potentialrelative to the grid structure as to vary the number of electronsimpinging the target anode.

It is another feature of this invention to utilize the individual gridwires as a portion of a delay line to provide distributed inductance andto bias the grid to cutofi' prior to application of a voltage pulse tothe delay line sufficient to bring the voltage above the cutoff level.

A complete understanding of this invention and of these and variousother features thereof may be gained from consideration of the followingdetailed description and the accompanying drawing in which:

Fig. 1 is a perspective view, partially in schematic form, of oneillustrative embodiment of this invention;

Fig. 2 is a series of schematic and graphical repre sentationsdemonstrating the effect of potential gradients present across thevarious grids of the embodiment of Fig. 1;

Fig. 3 is a portion of the grid structure of Fig. 1 in' bodiment of Fig.

Fig. 7 is a schematic representation of a depth measuring systemincorporating one illustrative embodiment of this invention; and

Fig. 8 is a schematic representation of a code conversion systemincorporating one illustrative embodiment of this invention.

Referring now to the drawing, Fig. 1 is a perspective view .of the basiccomponents of one illustrative embodiment of this invention. As theredepicted, an electron discharge device comprises a flat cathode member 1of sufficient size to provide a flooding beam, when energized by heaterelement 2, which will blanket substantially the entire surface of anodemember 3. Positioned between the cathode 1 and anode 3 is a series ofgrid members 4, 5, 6 and 7, arranged to provide coordinate positioningand, if desired, intensity modulation of the flooding beam. Each gridadvantageously comprises a frame 8 and a series of fine conductive wires9 fastened to the frame 8 so as to maintain the wires 9 mutuallyparallel to one of two control coordinates. Thus, in this illustrativeembodiment the wires 9 in the grids 4 and 5 are parallel to the verticalcoordinate so as to control the flooding beam incident on the anode 3 inthe horizontal direction while the wires 9 in the grids 6 and 7 areparallel to the horizontal coordinate so as to control movement of theflooding beam in the vertical direction. The wires 9 in each of gridmembers 4-7 are fastened in insulating material at one side of the frame8 and at regular intervals to a conductive element'll) which provides agraduated resistance across the opposite side of frame 8. The ends ofeach of the conductive elements 10 are connected to voltage sources soas to establish a potential gradient across the conductive element 10.

The grids 4 and 5 have their respective conductive ele ments 10oppositely connected to a source of potential, such that the potentialgradients established across these grids are oppositely directed.Similarly, grids 6 and 7 are oppositely connected to a potential sourceto provide oppositely directed potential gradients thereacross.

The anode member 3 advantageously may serve as the viewing screen forthis device and thus would comprise a transparent material such as glasshaving a transparent conducting film on the inner surface thereofadjacent grid 7 and having a luminescent material deposited on thetransparent conducting film. In thisfashion electrons of the floodingbeam impinging upon the inner surface of anode 3 will activate theluminescent material so as to provide a visual recording of the desiredpattern.

Fig. 2 provides a pictorial representation of a simple method forestablishing potential gradients across the grids 4 and 5. As depictedtherein, each of the grids 4 and 5 is provided with a source ofpotential indicated by battery 20. As shown, the negative side ofbattery is connected to the extreme left side of the grid 4 and to theextreme right side of the grid 5. In this manner oppositely directedpotential gradients. may be established on these grids.

A simple means for varying the potential gradient position with respectto cathode potential is indicated in Figs. 2b and 20 by the resistanceelements 21 and the moving contacts 22 connected to cathode potential,ground in this instance. Each resistance element 21 is connected inparallel with the battery 20 and a conductive element 10 so that varyingthe positions of the contacts 22 will vary the positions relative toground of the potential gradients established across the conductiveelements 10 and thus.

across the grid wires 9.

The means indicated in Fig. 2 for varying the potential gradientposition is merely illustrative and may take any number of forms wellknown in the art including electronic means for extremely rapidvariations.

In Fig. 2b the contact 22 has been set at a particular point on theresistance element 21, which setting establishes a potential gradientacross grid 4, shown graphically in Fig. 2d. Similarly, the setting ongrid 5, as shown in Fig. 2c, establishes the potential shown in Fig. 2e.Thus it is seen that a portion of the conductive grid Wires 9 is at anegative potential and a portion is at a positive potential with respectto the cathode, and at a discrete area, the potential is zero withrespect to the cathode, or ground potential in this instance. With thepotential gradients oppositely directed, as shown in Figs. 2d and 2e,the cathode potential is established in the same discrete areaon each ofthe grids 4 and 5. The flooding beam, in attempting to pass through thegrids 4 and 5, will encounter a negative potential on a portion of grid4 which will prevent its passage therethrough. However, the positiveportion of the grid will pass a portion of the flooding beam to grid 5.As indicated in Fig. 2e, the portion of the beam passing through grid 4will encounter that portion of grid 5 which is at a negative potential,so that only that portion of the flooding beam directed at the discretearea of each of grids 4 and 5 at cathode potential will be permitted topass through to grid 6.

At this point it is evident that only a line or ribbon beam will beavailable beyond grid 5, as shown in Fig. 2 The grids 6 and 7, Fig. 1,have potential gradients established thereacross in a manner so as tocontrol the vertical coordinate. These gradients are also oppositelydirected such that the portion of the original flooding beam passingthrough grids 6 and 7, Fig. 2], will be further confined so as toimpinge anode 3 at a discrete point. By varying the potential gradientson the grids 4-7 in accordance with a preestablished scanning pattern,it is seen that the original flooding beam may be scanned over the anode3 as a fine pencil beam in accordance with any desired pattern.

In order to avoid the detrimental effects of'drawing excessive gridcurrent when a large area of any one of the grids 4-'7 is positive,series limiting resistances advantageously may be added to the gridconductors, such as resistance 25 on the grid wires 9 in Fig. 3.

Fig. 4 illustrates the application of the grid control of this inventionfor varying the intensity of the beam incident on the anode 3. The grid4 has its moving contact 22 connected to ground through the switchingmechanism 40, Fig. 4a, which advantageously may vary the reference levelof grid 4. Grid 5 has its moving contact 22 connected directly tocathode potential, ground in this instance, as its reference level. Byvarying the relative reference levels, the size of the transmittedportion of the beam may be varied. Thus, with the switch in position 41,Fig. 4a, the potential gradients E and E formed by the grids 4 and 5,respectively, in effect will cross at a point at which the gridpotential is more negative than the cathode potential, as shown in Fig.4b. As is evident from this graphical representation, the flooding beamwill be completely cut off at this setting of the potential gradients.Movement of the switch con trol to contact 42 connects the grid 4 to thecathode potential which is at ground in this instance, establishing thepotential gradient positions shown in Fig. 40. With the setting atcontact 42 in Fig. 4a, the beam will pass through the discrete area ofgrids 4 and 5 at the cathode potential, providing the line or ribbonbeam output illustrated in'Fig. 2f. Again, moving the switch to contact43 in Fig. 4a, in effect, will cause the potential gradients of thegrids 4 and 5 to cross at a potential more positive than'that on thecathode, as shown in Fig. 2d, so as to permit a wider ribbon beam, asshown by the shaded area, to pass through the grids; i.e., electronspassing through portions of each grid 4 and 5 at or above cathodepotential. In this fashion the proportion of the beam incident on theanode 3 may be varied in accordance with any desired pattern. Similarly,variations conducted in this fashion on the grids 6 and 7 will providevariations in the size of a pencil beam incident on the anode 3.

Fig. 5 is one illustrative embodiment of this invention utilizing adelay line as an integral part of the novel grid control arrangement. Asthere depicted, only three grids 50, 6 and 7 are employed such that theflooding beam is controlled in only one of the horizontal and verticalcoordinates in the manner described hereinbefore. Thus, the grids 6 and7 in this example will control the vertical coordinate and will pass, inthe absence of grid 50, a ribbon beam to the anode 3 and sweep thisribbon beam thereacross. The control for this vertical sweep is providedby source 55 through transformer primary coil 56 and the varioussecondary coils 52. The coils 52 also pass steady state potential to thegrids 6 and 7 from sources 58 and 59 to form the requisite potentialgradients. The secondary coils 52 are so arranged as to provide the sameinstantaneous induced voltage to each end of the grid to which they areconnected, thus raising or lowering the potential gradient position onthe grid in relation to the cathode potential.

The two positioning grids 4 and 5 shown for the horizontal coord nate inFig. l are replaced in Fig. 5 by a single grid 50 connected to orforming a portion of a delay line. By applying a fixed linear horizontaltime base from a horizontal pulse generator 54 to this delay line grid50, which is biased so as to place the tube in a normal cut oficondit'on, the grid 50 may be pulsed so as to permit conduction only ina discrete linear area, which pulse would then move down the delay linegrid 50 toward its termination 51, continually changing the conducingarea and thereby providing a linear scan. The delay advantageously maybe distr.buted along the line, which delay will be made equal to thetime for one sweep of the input signal.

One possible delay line grid structure is illustrated in Fig. 6. In thisinstance there is shown a grid structure 50, the frame of whichsurrounds the cathode 1 and its heater. The front face of the grid framehas attached thereto the grid wires which in this instance forminductance for the delay line. The rear face of the grid frameis spacedintermediate metal plates 60 which form the necessary capacitance forthe delay line. In this fashion the grid 50 itself forms a distributeddelay line. Impulses from a pulse generator will travel down this lineso as to increase the potential on each grid wire in turn to causeconduction through the discrete area about the grid wire affected. Thedelay of the line illustrated in Fig. 6 is set equal to the time for onesweep of the input signal and is terminated in its characteristic impedance in order to prevent reflections.

To compensate for attenuation of the signal pulse traveling through thedelay line of grid 50, a saw-tooth voltage wave form advantageously maybe applied to the delay line or to the cathode 1 from the source 53,Fig. 5, to assure that each signal pulse, though of declining amplitude,will produce conduction. The source 53 may also be utilized tocompensate for the change in cathode potential resulting from the changein area of conduction during the vertical sweep. Thus it may be seenthat the circuit of Fig. 5 may have scanning application utilizing acombnation of the delay line grid 50 and the two grid verticalpositioning system.

In Fig. 7 is shown an adaptation of this grid control structure fordepth measurement. The circuit includes the usual components of sonarequipment including a transmitter 70, transducers 71 and 72 fortransmitting the signals from the transmitter 70 and receiving theechoes of these signals from an object beneath the surface of 6 thewater, and a receiver 73 which provides the echo signals from transducer72 to transformer 74. The output of transformer 74 varies the signal oncathode 75 of an indicator tube. The cathode 75 is elongated andpreferably in cylindrical form surrounded by slotted cylindrical gridsupport structures. The wires of grids 76 and 77 are stretched acrossthe windows formed by the grid support structures arranged in aconcentric form, such that a portion of the electrons emanating fromcathode 75 passes through grids 76 and 77 in turn. A tubular glassenvelope surrounds the entire structure of the indicator tube and theportion of this envelope adjacent the grid 77 has its inner surfacecoated with a luminescent material and forms the anode 78 which isplaced at a high positive potential with respect to the cathodepotential. The ends of grids 76 and 77 are connected to steady statepotential sources shown as batteries 80 and 81 in Fig. 7 so as toprovide oppositely directed potential gradients across the grids 76 and77 in the manner described hereinbefore. A timing-generator 82synchronizes the action of transmitter 70 and a sweep generator 83which, through transformer 84, varies the position of the potentialgradients across the grids 76 and 77 in relation to the cathodepotential. By providing a graduated scale adjacent the viewing screenanode 78 of the indicator tube, a direct indication of the distance tothe object sounded is available. 7

The versatility of this novel grid structure is further demonstrated bythe application disclosed in Fig. 8. In this circuit a structure similarto that shown in the sonar application of Fig. 7 is provided, but theanode structure is divided into discrete sections 86. With thisalteration the circuit may have application in various code conversionsystems such as required for time division multiplex operations. In thisinstance a video signal in time multiplex form is received intransformer and is fed therefrom to the cathode 87 of the convertertube. A sawtooth voltage applied by sweep generator 91 to grids 88 and89 through transformer 92 serves to move the conducting area to becoincident with a proper one of the anodes 86 during each time slot. Aconverter tube thus may be arranged to be nonconducting unless a pluse,present in the incoming code, coincides with signal pulses received attransformer 90 from a clock signal source 93. The incoming encodedsignal in pulse time multiplex form thus is readily converted toparallel form by the converter tube utilizing the novel grid structureof this invention.

Accordingly, it is to be understood that the described arrangements aremerely illustrative of the application of the principles of theinvention. Numerous other arrangements may be made by those skilled inthe art without departing from the spirit and scope of this invention.

What is claimed is:

1. An electron discharge device comprising a cathode, grid means and atarget anode arranged in that order within an evacuated envelope, saidgrid means comprising a plurality of mutually parallel wires, a distinctresistance member connected at discrete intervals to one end of each ofsaid wires and means applying a potential to said resistance member tocontrol the potential on adjacent ones of said grid wires whereby aportion of the electrons emitted by said cathode is intercepted bycertain of said grid wires and the balance impinges a discrete area ofsaid target.

2. An electron discharge device comprising in an evacuated envelope acathode, a target and grid means for controlling the flow of electronsfrom said cathode tosaid target, said grid means comprising a pluralityof parallel wires mutually interconnected at one end of each wirethrough an electrically conductive path, means applying a potential tosaid grid means through said electrically conductive path, and means insaid path including impedance means effective to control the potentialon ,7 adjacent ones of said grid wires so as to intercept aportion ofthe electrons emitted by said cathode at certain of said grid wires andto pass the balance of emitted elec trons to a discrete area of saidtarget.

3. An electron discharge device comprising an electron source, a targetand grid means positioned between said source and said target, said gridmeans comprising a plurality of wires connected at one end of each wireto an electrically conductive path, impedance means in said pathdistributed equally between the connecting ends of said wires, meansapplying potential to said grid means through said path, and means insaid path including said impedance means to control the potential onadjacent ones of said grid wires so as to intercept electrons .from saidsource to said target and passing adjacent a portion of said grid wires.

4. An electron discharge device comprising .a source of electrons, atarget and control means positioned in the path of electrons travelingfrom said source to said target, said control means comprising first andsecond grids each having a resistive member and a plurality of distinctmutually parallel grid wires connected to adjacent grid wires at one endthrough equal portions of said resistive member and insulated fromadjacent grid Wires at the other end, and means applying a potential ofone polarity to said first grid resistive member and of oppositepolarity to said second grid resistive member whereby electrons fromsaid source impinge said target at a discrete area thereof. p a

5. An electron discharge device in accordance with claim 4 furthercomprising means for varying the poten tial of said cathode with respectto the potential on each -:of said grid wires whereby saidtarget'isscanned by impinging electrons.

6. An electron discharge device in accordance with claim 5 furthercomprising means for varying the potential of said cathode with respectto the potential applied to said resistive members whereby the number ofelectrons impinging said target may be varied.

7. An electron discharge device in accordance with claim 6 wherein saidcontrol means further comprises third and fourth grids each having aresistive member and a plurality of distinct mutually'parallel gridwires connected to adjacent grid wires at one end through equal portionsof said resistive member, saidthird and fourth grid wires beingangularly displaced with respect to said first and second grid wires,and means applying a potential of one polarity to said third grid and ofopposite polarity to said fourth grid.

8..An electron discharge device in accordance with claim 7 wherein saidgrids are arranged in mutually parallel planes, the wires of saidfirstand second grids being displaced degrees with respect to the wiresof means connected to said inductive elements on the oppo site side ofsaid source, and meansiforapplyinga .voltage pulse to ,each of saidinductive elements;

10. An electron discharge .device in accordance with claim 6 whereinsaid control means further comprises pulse delay means including a thirdgrid of parallel grid wires angularly disposed with respect to saidfirst and second grid wires, .means biasing said delay means to cutofi,:and means for applying a voltage pulse consecutively to each of saidthird grid wires.

11. An electron discharge device comprising a source of electrons, atarget and control means comprising delay line means havinginterconnected inductive and capacitive means, said inductive meanscomprising parallel conductive elements arrayed as a grid between oneside of said source and said target and said capacitive means comprisinga pair of parallel plates positioned on the opposite side of saidsource, and means for applying a voltage pulse to each of saidconductive elements in succession.

12. An electron discharge device in accordance with claim 11 and furthercomprising means applying a sawtooth voltage wave form to said delayline means to compensate for attenuation of said voltage pulse alongsaid delay line means.

References Cited in the file of this patent UNITED STATES PATENTS

